In integrated circuits, the decrease in technology scaling is causing the design window for ESD protection devices to correspondingly shrink. Smaller and thinner devices also lead to the metal resistances of wires used in the devices to increase, which leads to a higher voltage drop over the metal wirings, which makes it difficult to clamp voltages during ESD events. As devices get smaller and thinner, the threat of ESD increases; however, it becomes increasingly difficult to make effective ESD protection devices.
ESD protection is of particular concern for source serial termination (SST) transmitters, such as the SST transmitter 1 shown in the integrated circuit 100 of FIG. 1. SST transmitter 1 includes an ESD protection structure 5. The ESD protection structure 5 includes an ESD protection device 6 that provides protection between the power supply 12 (“POWER_PAD”) and the output 11 (“IO_PAD”), an ESD protection device 7 that provides protection between the output 11 and ground (“GROUND_PAD”), and an ESD protection device 8 that provides protection from power supply 12 to ground. However, due to the size restrictions on ESD protection structure 5, ESD protection structure 5 may not be effective in clamping the voltage during an ESD event.